Halophilic microorganisms are responsible for the rosy discolouration of saline environments in three historical buildings with mural paintings

• Published in: PloS one 2014-08, Vol.9 (8), p.e103844-e103844
• Main Authors: Ettenauer, Jörg D, Jurado, Valme, Piñar, Guadalupe, Miller, Ana Z, Santner, Markus, Saiz-Jimenez, Cesareo, Sterflinger, Katja
• Format: Article
• Language: English
• Subjects: 12th century; Actinobacteria; Archaea; Bacteria; Biodegradation; Biodeterioration; Biofilms; Biology and Life Sciences; Biotechnology; Building materials; Buildings; Coloring Agents - metabolism; Communities; Construction materials; Cultural heritage; Culture media; Discoloration; Ecology and Environmental Sciences; Gypsum; Gypsum plaster; Halobacterium - genetics; Halobacterium - isolation & purification; Halococcus - genetics; Halococcus - isolation & purification; Historic buildings; Historic buildings & sites; Historical buildings; History, Ancient; History, Medieval; Inoculation; Life sciences; Limestone; Media (culture); Memorials & monuments; Microbial activity; Microbiota; Microbiota (Symbiotic organisms); Microorganisms; Natural resources; Paint - microbiology; Paintings - history; Research and analysis methods; Romanesque; Saline environments
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0103844

A number of mural paintings and building materials from monuments located in central and south Europe are characterized by the presence of an intriguing rosy discolouration phenomenon. Although some similarities were observed among the bacterial and archaeal microbiota detected in these monuments, their origin and nature is still unknown. In order to get a complete overview of this biodeterioration process, we investigated the microbial communities in saline environments causing the rosy discolouration of mural paintings in three Austrian historical buildings using a combination of culture-dependent and -independent techniques as well as microscopic techniques. The bacterial communities were dominated by halophilic members of Actinobacteria, mainly of the genus Rubrobacter. Representatives of the Archaea were also detected with the predominating genera Halobacterium, Halococcus and Halalkalicoccus. Furthermore, halophilic bacterial strains, mainly of the phylum Firmicutes, could be retrieved from two monuments using special culture media. Inoculation of building materials (limestone and gypsum plaster) with selected isolates reproduced the unaesthetic rosy effect and biodeterioration in the laboratory.